The study from The Queen's Medical Center in Hawaii involved 54 patients who had their hemoglobin/hematocrits compared to results from blood samples at the central laboratory as well as the results of normalized hematocrits determined actual blood volume measurements using the Daxor BVA-100. The study was presented at the 42nd Critical Care Congress. The hemoglobin/hematocrit tests are the most common blood test performed in medicine and surgery. These tests measure the concentration of red cells as a percentage in a blood sample. A normal male hemoglobin is 15% and a normal hematocrit is 45%, or a ratio of 1:3. These tests are often used interchangeably.

A major problem with the test is that it only is accurate when used in a patient who has a normal blood volume. In a patient who has a decreased blood volume, for example, the test will under estimate the amount of blood loss. Such a patient may have a sudden collapse of the circulation because the degree of blood loss was unrecognized. In contrast, in a patient who has an expanded blood volume due to excessive salt water administration, the blood cells may be diluted and the degree of blood loss over estimated and the patient possibly treated with an unnecessary transfusion.

In this study patients were measured by Pulse CO-Oximetry manufactured by the Masimo Corporation which provides a non-invasive continuous measure of the hemoglobin concentration through a specialized probe applied to the skin. These results were then compared to the laboratory results obtained utilizing actual blood samples. These critically ill patients then had their blood volume measured, which provides a true measure of the amount of red blood cells and plasma that a patient has. The BVA also then determines what the patient's normalized hematocrit is. This is the hematocrit/hemoglobin that reflects the true red cell volume status of the patient. The comparison of the hematocrit/hemoglobin with the central laboratory's hematocrit/hemoglobin showed a relatively wide scatter. The FDA has considered this difference acceptable and this instrument is approved for this use. The results were then compared to the normalized hematocrit/hemoglobin or true hematocrit. The findings of the study showed there was a better correlation with the non-invasive hemoglobin measurements and the measurements obtained from actual direct blood volume measurement. There was a wider scatter of results when the non-invasive instrument (Masimo) was compared to results from the central laboratory.

The results of this study show that when combining the results of the Pulse CO-Oximetry instrument with the variation from the true normalized hematocrit, it is possible to have a variation of approximately ±4 hematocrit points. This can translate into a clinical error of estimating the patient's blood volume status of ±18%. Septic patients have reported death rates of 20 - 40%. These results, combined with other published studies, have demonstrated from other institutions (such as Columbia College of Physicians and Surgeons) that physicians have a relatively low degree of accuracy in assessing a patient's blood volume status from indirect measures.

The ability to obtain continuous hemoglobin which can be converted into hematocrit measurements has the potential for monitoring major shifts in blood volume. However, such changes have not only limited value but can be highly misleading without an actual measurement of a patient's blood volume. In a previous publication involving blood volume study measurements from the Cleveland Clinic, Dr. Fetnat Fouad-Tarazi published a study on over 500 patients which documented the extreme variability for any specific hematocrit level with respect to blood volume. For example a patient with a hemoglobin/hematocrit of 25% could be 20% volume expanded or they could be 20% volume depleted. Therefore it can be very misleading to utilize hemoglobin/hematocrit levels for evaluating blood volume changes without knowing the actual blood volume of a patient. Dr. Joseph Feldschuh, President of Daxor Corporation and a cardiologist, noted that the use of a continuous hemoglobin monitor combined with a direct blood volume measurement can greatly improve a physician's understanding of the blood volume derangements that are commonly seen in surgical patients.

Dr. Mihae Yu, one of the senior authors of this study, previously had an article published in Shock (A Prospective Randomized Trial Using Blood Volume Analysis in Addition to Pulmonary Artery Catheter, Compared with Pulmonary Artery Catheter Alone, to Guide Shock Resuscitation in Critically Ill Surgical Patients, Shock, Vol. 35, No. 3, pp. 220-228, 2011), which showed the different survival rates in 100 patients (a death rate of 8% for the patients whose treatment was guided by blood volume measurement vs. 24% death rate in a control group whose treatment was guided by the usual clinical laboratory parameters without blood volume measurement).

A representative of Daxor will be in contact with Masimo to determine if there is an interest in collaborative studies to determine if there is a beneficial potential synergy between the two instruments for monitoring critically ill patients.

Daxor Corporation manufactures and markets the BVA-100, which is used in conjunction with Volumex, Daxor's single use diagnostic kit. For more information regarding Daxor Corporation's Blood Volume Analyzer BVA-100, visit Daxor's website at www.Daxor.com.